This invention relates to backlight panels, in particular to panels with changeable pictures.
There are known electrooptic displays with static or semi-dynamic pictures or signs comprising a plurality of display elements and based on various electrooptically active (EOA) substances. Hereinafter, xe2x80x9cEOA substancexe2x80x9d is meant to denote any substance capable of changing its optic properties such as color, transparency, reflectivity, etc., or capable of emitting light, in response to changes of applied electric or electromagnetic field, and thereby suitable for displaying images.
For example, U.S. Pat. Nos. 3,531,676 and 3,571,647 disclose electroluminescent panels with one common grid electrode and a plurality of separated grid electrodes which may be in the form of bars, letters, or decorative designs. Those separated electrodes may be powered independently, by a suitable electronic driver, thereby producing light effects of display elements going on and off.
The electrodes may be made of transparent conductive materials such as indium tin oxide layer deposited on a polymer film, as disclosed in WO 97/48254.
The display elements of such electrooptic display may be numerous and may form quite complex pictures capable of presenting animated images or alpha-numeric characters, such as LCD of calculators or hand-held computer games.
These displays, however, are static in the sense that the individual pictures cannot be changed but only the display elements"" optic effect can be controlled. Once manufactured, they can show permanently or periodically only one picture defined by the pattern of its display elements.
An ultimate solution to obtain dynamically changeable image is the matrix display where each picture element is formed of a plurality of pixels which may be controlled individually. However, these displays are very expensive. They have relatively low brightness due to the very process of pixel control (scanning) which limits the time during which a pixel can emit light.
In accordance with the present invention, there is provided an electrooptical display comprising two patterned elements: a picture element having a pattern of transparent translucent, re-emitting or reflective picture parts and a first electrode element having a pattern of separated electrodes. The pattern of separated electrodes matches the pattern of picture parts in a predetermined way. The display further comprises a carrying element, an electrooptically active (EOA) element and a second electrode element. Hereinafter, an EOA element is understood as a layer of EOA substance with or without a carrying substrate. The electrode elements and the EOA element form a plurality of EOA zones corresponding to the pattern of separated electrodes and define, together with the picture parts, a visible image. The patterned elements are detachably attachable, preferably by means of adhesive layers, and thereby allow the electrooptic display to display different images using the same carrying element and the same EOA element. The patterned elements may also consist of a plurality of parts that can be arranged and attached in various ways.
The patterned picture elements may be organized in changeable pairs with matching patterned electrode elements. Moreover, a picture element and an electrode element may be integrated in one changeable element. The electrode elements may be transparent or translucent, for example made of indium tin oxide, or may be formed as a network of thin metal strips deposited on a polymer substrate.
In accordance with one aspect of the invention, the electrode elements are disposed on different sides of the EOA element. The second electrode is a common electrode for all separated electrodes, whereby each of the separated electrodes defines an EOA zone including a portion of the EOA substance and a portion of the common electrode.
In accordance with another aspect of the invention, the first and the second electrode elements are both patterned and are disposed on one side of the EOA element, in the form of conductive paths running parallel to each other and free of contact with each other. The conductive paths preferably have the form of spirals or of combs inserted into each other. Both electrode elements and the picture element may be integrated in one changeable element. In this case EOA zones are formed in that part of the EOA element which is penetrated by the electric field formed by two adjacent conductive paths belonging to different electrodes.
The adhesive layers are preferably transparent and conductive. A conductive adhesive layer on the pattered electrode is laid in separated spots corresponding to the electrode pattern. Two adhesive layers intermediate to the changeable patterned element and one of the other elements may be used, where each adhesive layer is firmly attached to one element and the attaching and detaching takes place between the two adhesive layers.
To provide for better electrical contact between the electrode elements and the EOA element, one or more z-conductive layers may be disposed therebetween. A z-conductive layer is characterized by good conductivity across its thickness and zero or low conductivity parallel to the layer. Such material is described, for example, in WO/0036649 and WO98/57226. The z-conductive layers may also be transparent and/or adhesive.
The electrooptic display of the present invention provides for an efficient and cheap display device with versatile functions. The same EOA element and the same carrying element may be used to obtain various images with attractive optic effects. Pictures or parts thereof may be peeled off and attached as easy as wallpaper. All elements of such pictures may be individually controlled by a suitable electronic circuitry, such as digital controllers, computers, etc.